A conventional inspection apparatus includes: a movable mounting table for mounting thereon, e.g., an inspection target (e.g., wafer); a probe card having a plurality of probes, disposed above the mounting table; a temperature control unit for controlling a temperature of the mounting table; an alignment unit for aligning the probes of the probe card and a plurality of electrode pads of the wafer on the mounting table; and a control unit for controlling the mounting table, the temperature control unit and the alignment unit. The conventional inspection apparatus is configured to control the wafer on the mounting table to a predetermined temperature by the temperature control unit and bring the electrode pads of the wafer into electrical contact with the probes of the probe card under the control of the control unit, to thereby inspect electrical characteristics of a plurality of devices formed on the wafer by a predetermined contact load.
Therefore, the inspection apparatus performs high-temperature inspection by heating a wafer to a temperature of, e.g., about 150° C., or low-temperature inspection by cooling an inspection target to a temperature of, e.g., about minus several tens of degrees Celsius. In the case of performing the high-temperature inspection or the low-temperature inspection, the wafer is heated or cooled to a predetermined inspection temperature by using a temperature control unit built in the mounting table, and the mounting table is raised by a vertical drive mechanism to bring the devices into contact with the probes by a predetermined contact load.
When the electrical characteristics of the wafer are inspected under a high temperature of, e.g., about 150° C., the wafer is heated to a high temperature of about 150° C. by the temperature control unit in an initial stage of the inspection. Since, however, the probe card is not heated, the wafer and the probe card have a large temperature difference. Therefore, when the first device and the probes are brought into contact with each other by a predetermined contact load, the probe card is heated by heat emitted from the wafer during the inspection. As a consequence, the probe card is thermally expanded gradually, and tip heights of the probes are changed by several tens of μm. Since the contact load with respect to the wafer becomes excessive, the reliability of the inspection deteriorates. In some cases, the devices or the probes may be damaged.
Hence, in a conventional inspection method, as shown in FIG. 5, for example, the mounting surface of the mounting table 1 is moved toward the probe side 2 to a position spaced from the tip positions of the probes 2A of the probe card 2 by a distance of about 5 (e.g., several hundreds of μm) (separated distance), and the probe card 2 is pre-heated and thermally expanded by the heat emitted from the pre-heated mounting table 1. When the tip positions of the probes 2A are not changed any more, the electrical characteristics of the wafer are inspected.
The pre-heating of the probe card 2 and the inspection of electrical characteristics of the wafer are carried out in accordance with the flowchart shown in FIG. 6, for example. Specifically, in order to initiate inspection of a wafer in any lot, first, the mounting table 1 is moved to carry out alignment of the probes 2A of the probe card 2 by using the a CCD camera 3 provided at a side of the mounting table, and the tip positions of the probes 2A are detected (step S1). Then, it is waited until the mounting table 1 reaches a predetermined temperature (substantially equal to the temperature of the mounting table) (step S2). When the mounting table 1 reaches the predetermined temperature, the mounting table 1 is moved to a position immediately below the probe card 2 as shown in FIG. 5 and then raised to and stopped at a position separated from the tip positions of the probes 2A by a distance of several hundred μm. In that position, the probe card 2 is pre-heated by the heat emitted from the mounting table 1 (step 3). Upon completion of the pre-heating, the probe alignment is performed by using the CCD camera 3 (step S4). Next, a probe grinding wafer is mounted on the mounting table 1, and the probes 2A are polished by using the probe grinding wafer on the mooting table 1 (step S5). Upon completion of the grinding operation, the probe alignment is performed to detect the tip positions of the probes (step S7). Thereafter, a target wafer of the corresponding lot is transferred and mounted on the mounting table 1 (step S8). Next, the electrical characteristics of the wafer are inspected.
Meanwhile, in the conventional inspection method, the pre-heating requires several tens of minutes or a longer period of time such as several hours depending on types of probe cards, which results in decrease of practical operation time of the apparatus. Further, in the conventional pre-heating, there is no function of detecting whether or not the probe tip height is stable. Therefore, the pre-heating is executed for a sufficient period of time regardless of types of probes, or the pre-heating is executed by calculating the estimated time of the pre-heating for each type of probe cards.
Accordingly, there have been proposed various methods capable of effectively performing pre-heating in a short period of time. For example, Japanese Patent Application Publication No. 2007-088203 discloses a technique for pre-heating a probe card by bringing a plurality of probes of the probe card into direct contact with a wafer whose temperature is adjusted to a predetermined inspection temperature and thermally stabilizing the probe card in a short period of time. Further, Japanese Patent Application Publication No. 2004-266206 discloses a technique for installing a heat plate for pre-heating on a movable supporting table provided in addition to the mounting table for the wafer and performing pre-heating by bringing the heat plate for pre-heating into direct contact with the probe card by moving the supporting table.
However, in the technique of Japanese Patent Application Publication No. 2007-088203, the position of the mounting table is corrected such that the probes are brought into contact with the wafer by a predetermined distortion amount based on the inspection temperature of the wafer and the elapsed time after the contact between the probes and the wafer. Therefore, the elapsed time after the contact of the probes with the wafer and the extension/contraction length data of the probes need to be collected at predetermined time intervals before the inspection of the wafer, and the data indicating the correlation between the elapsed time and the position correction value need to be created based on the collected data. In the technique of Japanese Patent Application Publication No. 2004-266206, the supporting table for supporting the heat plate for pre-heating should be provided in addition to the mounting table for the wafer, which results in scaling up of the inspection apparatus. Further, the low-temperature inspection for inspecting the wafer at a temperature of, e.g., about minus several tens of degrees Celsius, has the same problems as those of the high-temperature inspection.